U.S. patent number 8,201,717 [Application Number 12/158,756] was granted by the patent office on 2012-06-19 for apparatus and method for melting and dispensing thermoplastic material.
This patent grant is currently assigned to Nordson Corporation. Invention is credited to Marcel Puffe, Leslie J. Varga.
United States Patent |
8,201,717 |
Varga , et al. |
June 19, 2012 |
Apparatus and method for melting and dispensing thermoplastic
material
Abstract
An apparatus for melting and dispensing thermoplastic material
is provided that includes an un-heated hopper having an inlet for
receiving particles of a thermoplastic material and an outlet for
discharging the particles and a heated manifold including at least
one cavity formed therein and having an inlet and an outlet the
inlet communicating with the outlet of the hopper for receipt of
the particles from the hopper. The hopper is disposed external of
the heated manifold. The heated manifold is effective for melting
the particles into molten thermoplastic material therein. The
apparatus further includes a pump having an inlet in fluid
communication with the cavity. An outlet of the pump is in fluid
communication with an inlet of a dispenser and an outlet of the
dispenser is effective for dispensing the molten thermoplastic
material therethrough.
Inventors: |
Varga; Leslie J. (Cumming,
GA), Puffe; Marcel (Nordrheinwestfahlen, DE) |
Assignee: |
Nordson Corporation (Westlake,
OH)
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Family
ID: |
38288367 |
Appl.
No.: |
12/158,756 |
Filed: |
January 16, 2007 |
PCT
Filed: |
January 16, 2007 |
PCT No.: |
PCT/US2007/060569 |
371(c)(1),(2),(4) Date: |
June 23, 2008 |
PCT
Pub. No.: |
WO2007/084891 |
PCT
Pub. Date: |
July 26, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080302477 A1 |
Dec 11, 2008 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60759305 |
Jan 17, 2006 |
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Current U.S.
Class: |
222/593;
222/590 |
Current CPC
Class: |
B05C
11/101 (20130101); B29B 13/022 (20130101); B05C
5/0225 (20130101); B29B 13/02 (20130101); B05C
9/14 (20130101); B05C 5/001 (20130101); E06B
3/9612 (20130101); B05C 5/0237 (20130101); B05B
12/006 (20130101) |
Current International
Class: |
B29C
65/40 (20060101) |
Field of
Search: |
;222/593,590 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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3815089 |
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Nov 1989 |
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DE |
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10156691 |
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May 2003 |
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DE |
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98/14314 |
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Apr 1998 |
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WO |
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Other References
European Patent Office, Supplementary European Search Report in EP
Appl. No. 07710140, Jan. 27, 2010. cited by other .
The State Intellectual Property Office of the People's Republic of
China, Office Action in Chinese Application No. 200780002535.0,
Apr. 14, 2010. cited by other .
U.S. Patent and Trademark Office, International Search Report and
Written Opinion in corresponding PCT Application Serial No.
PCT/US2007/60569, Oct. 3, 2007. cited by other.
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Primary Examiner: Johnson; Christina
Assistant Examiner: Liu; Xue
Attorney, Agent or Firm: Wood, Heron & Evans, LLP
Parent Case Text
CROSS-REFERENCES
This application claims the priority benefit of U.S. Provisional
Patent Application No. 60/759,305, "Apparatus for Melting and
Dispensing Thermoplastic Material", filed on Jan. 17, 2006, which
is expressly incorporated by reference herein in its entirety.
Claims
What is claimed is:
1. An apparatus for melting and dispensing thermoplastic material
comprising: an un-heated hopper having an inlet for receiving
particles of a thermoplastic material and an outlet for discharging
the particles; a heated manifold including at least one cavity
formed therein, said at least one cavity having an inlet
communicating with said outlet of said hopper for receipt of the
particles of the thermoplastic material from said hopper, said
hopper being disposed external of said heated manifold, said at
least one cavity further including an outlet communicating with a
pump supply passage, and further including a pump discharge
passage, said heated manifold effective for melting the particles
into molten thermoplastic material therein; a pump including an
inlet and an outlet, said inlet of said pump being in fluid
communication with said pump supply passage and with said outlet of
said at least one cavity, and said outlet of said pump being in
fluid communication with said pump discharge passage; and a
dispenser including an inlet and an outlet, said pump discharge
passage of said heated manifold being in fluid communication with
said inlet of said dispenser for delivering molten thermoplastic
material to said dispenser, said outlet of said dispenser effective
for dispensing the molten thermoplastic material therethrough.
2. The apparatus as recited in claim 1, wherein: said pump is
mounted on said manifold; and said dispenser is mounted on said
manifold.
3. The apparatus as recited in claim 1, further comprising: a
plurality of said cavities formed in said manifold, said cavities
spaced apart from one another, each said cavity having an inlet
communicating with said outlet of said hopper and an outlet; and a
collector passage fluidicly coupled with said outlet of each of
said cavities, said collector passage including an outlet in fluid
communication with said inlet of said pump.
4. The apparatus as recited in claim 3, wherein: said heated
manifold further comprises a plurality of fins, each of said fins
being disposed intermediate two adjacent ones of said cavities.
5. The apparatus as recited in claim 4, wherein: each of said fins
has a triangular-shaped cross-section with an apex extending into
said outlet of said hopper.
6. The apparatus as recited in claim 1, wherein: said hopper is
made of a polymeric material.
7. The apparatus as recited in claim 1, further comprising: an
un-heated hose coupled at one end to said inlet of said hopper and
having an opposite end effective for receiving the particles of
thermoplastic material therethrough.
8. The apparatus as recited in claim 7, wherein: said opposite end
of said hose is operatively coupled to a source of pressurized air
whereby said opposite end of said hose is effective for suctioning
the particles of the thermoplastic material from a supply reservoir
of the particles, said hose being effective for transporting the
particles to said inlet of said hopper when the pressurized air is
flowing within said hose.
9. The apparatus as recited in claim 8, wherein: said hopper
includes an upper portion comprising said inlet of said hopper and
further comprising a plurality of apertures formed therein and
disposed about a periphery thereof, said apertures being effective
for exhausting pressurized air entering said hopper from said
hose.
10. An apparatus for melting and dispensing thermoplastic material,
comprising: an un-heated hopper having an inlet for receiving
particles of a thermoplastic material and an outlet for discharging
the particles, said hopper further including a longitudinal axis; a
device effective for moving the particles of the thermoplastic
material around and along said longitudinal axis of said hopper and
through said outlet of said hopper; a heated manifold including at
least one cavity formed therein, said at least one cavity having an
inlet communicating with said outlet of said hopper for receipt of
the particles of the thermoplastic material from said hopper, said
hopper being disposed external of said heated manifold, said at
least one cavity further including an outlet communicating with a
pump supply passage, and further including a pump discharge
passage, said heated manifold effective for melting the particles
into molten thermoplastic material therein; a pump including an
inlet and an outlet, said inlet of said pump being in fluid
communication with said pump supply passage and with said outlet of
said at least one cavity, and said outlet of said pump being in
fluid communication with said pump discharge passage; and a
dispenser including an inlet and an outlet, said pump discharge
passage of said heated manifold being in fluid communication with
said inlet of said dispenser for delivering molten thermoplastic
material to said dispenser, said outlet of said dispenser effective
for dispensing the molten hot melt adhesive therethrough.
11. The apparatus as recited in claim 10, wherein: said device is
an auger disposed within said hopper.
12. The apparatus as recited in claim 10, wherein: said dispenser
is mounted on said heated manifold.
13. The apparatus as recited in claim 10, wherein: said pump is
mounted on said heated manifold.
14. The apparatus as recited in claim 11, wherein: said auger
includes a shaft and a helical blade integral with said shaft, said
blade having a substantially constant major diameter.
15. The apparatus as recited in claim 11, wherein: said auger
includes a shaft and a helical blade integral with said shaft, said
blade having a tapered major diameter.
16. The apparatus as recited in claim 10, further comprising: a
first motor drivingly coupled with said auger; and a second motor
drivingly coupled with said pump.
17. The apparatus of claim 1, further comprising: a connecting
structure operatively coupling said hopper to said manifold and
inhibiting heat transfer therebetween; wherein said connecting
structure further comprises a clamp.
Description
FIELD OF INVENTION
The present invention relates to apparatuses and methods for
melting and dispensing thermoplastic materials.
BACKGROUND
Thermoplastic materials include those materials that can be
repeatedly melted and cooled to a solid. Thermoplastic material
includes waxes and thermoplastic adhesives, also referred to as
"hot melt" adhesives, etc. "Hot melt" adhesives are used in a wide
variety of applications including the assembly of various types of
products including furniture, doors, windows, etc., and the closing
of boxes, containers, etc.
Typically, solid hot melt adhesive, in various shapes and sizes, is
supplied to a melter that includes a heated tank and/or a heated
grid to produce molten hot melt adhesive. Solid hot melt adhesive
can also be supplied in drums or barrels in which the adhesive is
melted by the use of a platen. After heating, the molten adhesive
is pumped through a heated hose, to maintain the molten material at
the required application temperature, to an applicator or
dispenser, sometimes referred to as a dispensing "gun" or gun, or a
gun module, comprising a valve and a nozzle. Heated hoses are
believed to be a primary source of charring problems associated
with hot melt adhesives, particularly in systems requiring
relatively low melt rates. In such applications, the residence time
of the molten adhesive within a heated hose can exceed the "pot
life" of the adhesive as a result of the relatively high volume of
molten adhesive within the hose and the relatively low usage rate.
"Pot life" as used herein is the maximum time at the system
temperature before the adhesive starts to degrade resulting in
increased viscosity and charring. Oversized tanks or other
reservoirs of molten adhesive can also contribute to this problem.
Exceeding the "pot life" of a thermoplastic adhesive may result in
operational problems, such as filter clogging, and the cleaning
required after charring has occurred.
It is desirable to provide an adhesive dispensing system that
reduces charring. It may also be desirable to provide an adhesive
dispensing system where the time the material is maintained at
elevated temperature is significantly reduced and/or the volume of
material is reduced. Finally, it may also be desirable to eliminate
the need of heated hoses for transporting liquefied hot melt.
SUMMARY
According to a first aspect of the present invention, an apparatus
is provided for melting and dispensing thermoplastic material that
may be a hot melt adhesive. The apparatus includes an un-heated
hopper having an inlet for receiving particles of a thermoplastic
material and an outlet for discharging the particles and a heated
manifold including at least one cavity formed therein. The at least
one cavity has an inlet communicating with the outlet of the hopper
for receipt of the particles of the thermoplastic material from the
hopper. The hopper is disposed external of the heated manifold. The
at least one cavity further includes an outlet. The heated manifold
is effective for melting the particles into molten thermoplastic
material therein. The apparatus further includes a pump having an
inlet and an outlet, with the inlet of the pump being in fluid
communication with the outlet of the at least one cavity. The
apparatus also includes a dispenser having an inlet and an outlet.
The outlet of the pump is in fluid communication with the inlet of
the dispenser, and the outlet of the dispenser is effective for
dispensing the molten thermoplastic material therethrough.
Various embodiments of the apparatus of the present invention can
also include one or more of the following features. For instance,
both the pump and dispenser can be mounted on the manifold. The
manifold can include a plurality of cavities formed in the
manifold, with the cavities spaced apart from one another and each
cavity having an inlet communicating with the outlet of the hopper
and an outlet. A collector passage can be fluidicly coupled with
the outlet of each of the cavities. The collector passage includes
an outlet in fluid communication with the inlet of the pump.
The hopper can be made of a polymeric material. A plurality of the
cavities can be formed in the heated manifold, with the cavities
spaced apart from one another and each having an inlet
communicating with the outlet of the hopper and further including
an outlet. In this embodiment, the collector passage can be in
fluid communication with the outlet of each of the cavities.
The apparatus can further include a plurality of fins, with each of
the fins being disposed intermediate of two adjacent ones of the
cavities. In one embodiment, the fins have a triangular-shaped
cross-section, with an apex disposed within the outlet of the
hopper.
The apparatus can further include an un-heated hose coupled at one
end to the inlet of the hopper and having an opposite end effective
for receiving the particles of the thermoplastic material
therethrough. More particularly, the opposite end of the hose is
operatively coupled to a source of pressurized air whereby the
opposite end of the hose is effective for suctioning the particles
of the thermoplastic material from a supply reservoir of the
particles. The hose is effective for transporting the particles to
the inlet of the hopper when the pressurized air is flowing within
the hose. In this embodiment, the hopper includes an upper portion
comprising the inlet of the hopper and further comprises a
plurality of apertures formed therein and disposed about a
periphery thereof. The apertures are effective for exhausting
pressurized air entering the hopper from the un-heated hose.
The apparatus can further include a device effective for moving the
particles of the thermoplastic material adhesive around and along
the longitudinal axis of the hopper and through the outlet of the
hopper. The device can be an auger with a blade having a major
diameter which can be either substantially constant or tapered. A
motor can be drivingly coupled with the auger.
According to a second aspect of the present invention, a method is
provided for melting and dispensing thermoplastic material,
comprising supplying particles of a thermoplastic material to an
un-heated hopper disposed external of a heated manifold,
discharging the particles of the thermoplastic material from the
hopper into the heated manifold, melting the particles of the
thermoplastic material into molten thermoplastic material within
the heated manifold, directing the molten thermoplastic material
through the heated manifold to a dispenser mounted on the manifold,
and dispensing the molten thermoplastic material from the dispenser
onto a workpiece.
In other embodiments, the method can also comprise one or more of
the following features. The particles of thermoplastic material can
be transported from a supply reservoir of the particles, through an
un-heated hose and to the inlet of the hopper. The particles can be
discharged from the hopper into the heated manifold solely by
gravity. A pre-determined level of the particles within the hopper
can be automatically maintained, and the hopper can be mounted on
the heated manifold.
According to an alternative embodiment, a method is provided
comprising supplying particles of a thermoplastic material to an
un-heated hopper having an outlet and a longitudinal axis, with the
hopper being disposed external of a heated manifold and moving the
particles around and along the longitudinal axis of the hopper to
discharge the particles through the outlet of the hopper and into
the heated manifold. The method further comprises melting the
particles into molten thermoplastic material within the heated
manifold, directing the molten thermoplastic material through the
heated manifold to a dispenser mounted on the manifold, and
dispensing the molten thermoplastic material from the
dispenser.
In various embodiments, the method can further comprise one or more
of the following features. The particles can be moved around and
along the longitudinal axis by an auger disposed within the hopper.
The molten thermoplastic material can be directed through the
heated manifold to a pump mounted on the manifold and pumped from
the pump through the manifold to the dispenser.
According to a third aspect of the present invention a method is
provided for bonding two members of a window sash to one another to
create a corner of the window sash, with the two members being
disposed in abutting relationship with one another. The method
comprises mounting an apparatus for melting and dispensing a hot
melt adhesive on a dedicated automation device, with the apparatus
comprising a heated manifold, an un-heated hopper disposed external
of and mounted on the heated manifold, a pump mounted on the heated
manifold and a dispenser mounted on the heated manifold. The method
further comprises supplying particles of a hot melt adhesive to the
un-heated hopper and discharging the particles of the hot melt
adhesive from the hopper into the heated manifold. The method also
comprises melting the particles of the hot melt adhesive into
molten hot melt adhesive within the heated manifold, directing the
hot melt adhesive through the heated manifold to the dispenser and
aligning the dispenser with an aperture formed in a first one of
the two members of the window sash, with the aperture being in
fluid communication with a first channel extending between the
interior of the first member of the window sash and the interior of
the second member of the window sash. The method further comprises
injecting the molten hot melt adhesive from the dispenser into and
through the aperture into the first channel.
According to a fourth aspect of the present invention, a method is
provided for bonding two ends of a filter to one another, the
filter being formed into a cylindrical shape with the two ends of
the filter being disposed in abutting relationship with one
another. The method comprises mounting an apparatus for melting and
dispensing a hot melt adhesive on a dedicated automation device,
the apparatus comprising a heated manifold, an un-heated hopper
disposed external of and mounted on the heated manifold, a pump
mounted on the heated manifold and a dispenser mounted on the
heated manifold. The method further comprises supplying particles
of a hot melt adhesive to the un-heated hopper, discharging the
particles of the hot melt adhesive from the hopper into the heated
manifold, melting the particles of the hot melt adhesive into
molten hot melt adhesive within the heated manifold and directing
the molten hot melt adhesive through the heated manifold to the
dispenser. The method also comprises aligning the dispenser with
the two ends of the filter and dispensing the molten hot melt
adhesive between the two ends of the filter to form a seam bonding
the two ends together.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features, aspects and advantages of the present
invention will become better understood with regard to the
following description, appended claims and accompanying drawings
wherein:
FIG. 1 is an isometric view of an apparatus for melting and
dispensing thermoplastic material according to the present
invention;
FIG. 2 is an isometric view similar to FIG. 1 but with the included
hopper shown in exploded assembly view to further illustrate the
included heated manifold;
FIG. 3 is a cross-sectional view taken along line 3-3 in FIG.
2;
FIG. 4 is a cross-sectional view taken along line 4-4 in FIG.
2;
FIG. 5 is a cross-sectional view similar to FIG. 3 illustrating an
alternative embodiment of an apparatus for melting and dispensing
thermoplastic material according to the present invention;
FIG. 6 is a cross-sectional view similar to FIG. 5 illustrating
another alternative embodiment of an apparatus for melting and
dispensing thermoplastic material according to the present
invention;
FIG. 7 is a plan view of a window including a window sash;
FIG. 8 is an enlarged view of the area circled in FIG. 7 further
illustrating one of the corners of the window, illustrating one
application of the apparatus of the present invention;
FIG. 9 is an isometric view of a filter illustrating another
application of the apparatus of the present invention;
FIG. 10 is an enlarged, fragmentary schematic representation of a
portion of the filter shown in FIG. 9; and
FIG. 11 is a perspective view illustrating one application of the
apparatus of the present invention.
DETAILED DESCRIPTION
Referring now to FIG. 1 and FIG. 3, an apparatus 10 for melting and
dispensing thermoplastic material such as hot melt adhesives is
illustrated. Although apparatus 10 can be used to dispense various
thermoplastic materials, it is particularly advantageous when used
to dispense hot melt adhesive, and the apparatus 10 will be
described herein in conjunction with this application. Apparatus 10
includes a hopper 12 having an inlet 14 (shown in FIG. 3) effective
for receiving solid particles of a hot melt adhesive, such as in
pellets or chicklets, from a supply reservoir or tank 16. In the
illustrative embodiment, the solid particles of the hot melt
adhesive are supplied to the inlet 14 of hopper 12 by an automatic
feed system 18 such as the FillEasy.TM. Adhesive Feed System or the
Fillmaster.RTM. Adhesive Feed System, both made by the Nordson
Corporation. As used herein the term "solid particles" refers to
particles that are in the solid state, not the liquid or molten
state. However, as may be appreciated by one skilled in the art,
solid particles can have varying degrees of hardness depending upon
factors such as exposure to atmosphere, for example. Accordingly,
some solid particles may be somewhat "soft to the touch". The
automatic feed system 18 includes an un-heated transport hose 20
coupled at one end 20a to the inlet 14 of hopper 12 and terminating
at an opposite end in a suction wand 22. A source of pressurized
air 24 is supplied to the suction wand 22 via one or more conduits
26. More particularly, the pressurized air is supplied to a venturi
pump (not shown) contained within the suction wand 22. The suction
wand 22 is disposed proximate the inlet of the supply reservoir 16
of the solid particles of the hot melt adhesive and the venturi
pump included in the suction wand is effective for suctioning the
solid particles of the hot melt adhesive out of supply reservoir 16
and into hose 20, and for transporting or pumping the solid
particles of the hot melt adhesive through hose 20 to the inlet 14
of hopper 12 via pressurized air.
Alternatively, a screw conveyor or other transport system can be
used to transport the solid particles of the hot melt adhesive from
supply tank 16 to the inlet 14 of hopper 12. As a further
alternative, the automatic adhesive supply system 18 can be
omitted, with the solid particles of the hot melt adhesive being
manually fed into the inlet 14 of the hopper 12. In this case, the
hopper can include a lid, which can be opened for manual supply of
the particles into the hopper 12 and be otherwise closed.
In the illustrative embodiment shown in FIG. 1, the hopper includes
a lower portion 28, intermediate portion 30 and upper portion 32.
The upper portion 32 is a hollow cylinder which is suitable for
accepting hose 20. The upper portion 32 includes a plurality of
apertures 34 formed therein and disposed about a periphery of the
upper portion 32. Each of the apertures 34 communicates with an
interior chamber 36 (FIG. 3) formed by the upper portion 32 of
hopper 12 and open onto an exterior surface 38 of the upper portion
32. Accordingly, apertures 34 are effective for exhausting
pressurized air entering chamber 36 from the hose 20, to the
atmosphere exterior of hopper 12.
Apparatus 10 includes a heated manifold 40 and hopper 12 may be
mounted to manifold 40 or closely coupled thereto. The lower
portion 28 of hopper 12 includes a peripheral flange 42 that is
disposed in contacting engagement with manifold 40. A clamp 44,
made of an insulating material, is configured to receive the
peripheral flange 42 and is used to mount the hopper 12 on manifold
40. The clamp 44 may be secured by a plurality of conventional
fasteners, such as bolts 46 (FIG. 1), which pass through apertures
(not shown) formed in the clamp 44 and into mating apertures 48
formed in the manifold 40, as best appreciated with reference to
the exploded assembly view shown in FIG. 2. The insulated clamp 44
is effective for maintaining the peripheral flange 42 of the hopper
12 at an acceptable temperature. Flange 42, as well as the
remainder of hopper 12 can be made of an insulating material. For
example, hopper 12 can be made of a polymeric material having a
relatively low thermal conductivity such as
polytetrafluoroethylene, commonly referred to as Teflon.RTM.. In
contrast, the manifold 40 is made of a metal having a relatively
high coefficient of conductive heat transfer, such as aluminum.
With reference to FIGS. 1 and 2, the periphery of the intermediate
portion 30 of hopper 12 may have an irregular shape that includes
two surfaces 50 that may be concave as shown. Alternatively,
surfaces 50 may be substantially flat-machined surfaces. A hole can
be formed in and extend through the intermediate portion 30 of
hopper 12 such that one end of the hole opens onto an interior
chamber 52 (FIG. 3) that is defined by the lower 28 and
intermediate 30 portions of hopper 12. The opposite end of the hole
opens onto one of the concave surfaces 50 of the intermediate
portion 30 of hopper 12. A level sensor 54 can extend through the
aperture formed in the intermediate portion 30 such that a distal
end of the level sensor 54 is disposed within the interior chamber
52. The distal end of the sensor 54 can be substantially flush with
an inner surface 58 of hopper 12. When the level of the solid
particles 56 of hot melt adhesive falls below the level sensor 54,
the sensor 54 can send a signal to a controller (not shown) that
controls the adhesive supply system 18 such that additional hot
melt adhesive is transported from the supply reservoir 16 through
hose 18 into hopper 12.
The opening in the bottom of hopper 12 can be larger than the
opening in the top of hopper 12, such that the inner surface 58 of
hopper 12 forms a relatively small angle 60, such as about
5.degree., with the vertical. This flared surface 58 facilitates
movement of the particles 56 of the hot melt adhesive through
hopper 12.
A plurality of heating elements 62 are disposed within manifold 40
and extend substantially therethrough as illustrated in FIGS. 3 and
4. In the illustrative embodiment, each of the heating elements 62
are electrical resistance heating elements. An electrical cord set
63 is provided that is electrically coupled to heating elements 62
and can be coupled to a source of electricity (not shown). Heating
elements 62 are effective for transferring heat substantially
throughout the manifold 40 via conduction. The particular
positioning of heating elements 62 within manifold 40 will be
discussed in greater detail subsequently.
A plurality of cavities 64 can be formed in manifold 40 and spaced
apart from one another. Each of the cavities 64 includes an inlet
66 (FIG. 4) that communicates with an outlet 68 (FIG. 3) of hopper
12. Accordingly, the solid particles 56 of the hot melt adhesive
are free to drop into the cavities 64 under the action of gravity.
The inlets 66 of the cavities 64 open onto an upper surface 70 of
manifold 40. Manifold 40 further includes a plurality of fins 72
that protrude upwardly from surface 70 and extend into the outlet
68 of hopper 12. Each of the fins 72 can have a triangular-shaped
cross-section with a sharp, upwardly pointing apex 74 at the
interface of two sides of the triangular shape of the fins 72. The
triangular shape of fins 72 helps guide the adhesive into cavities
64 and ensures that the solid particles are not impeded from
entering cavities 64. Additionally, the triangular shape of fins 72
provides increased surface area, relative to fins having a
rectangular cross-section for instance, which is advantageous with
respect to heat transfer to the adhesive. Since the hopper 12 is
un-heated it remains at ambient temperature with the exception of
the lowermost portion which receives heat transfer from the heated
manifold 40.
Melting occurs within cavities 64 and transforms the solid
particles into molten, hot melt adhesive, by the time the material
discharges from cavities 64. Each of the cavities 64 includes an
outlet 76 proximate the bottom of the corresponding cavity 64. Each
of the outlets 76 are in fluid communication with a collector
passage 78 formed in manifold 40. The molten hot melt adhesive
discharges from the collector passage 78 through an outlet 80 to a
pump supply passage 82. The pump supply passage 82 is in fluid
communication at one end with the outlet 80 of the collector
passage 78, and therefore with each of the cavities 64, and is in
fluid communication at the opposite end with an inlet 84 of a pump
86. As shown in FIG. 3, the pump supply passage 82 slopes
downwardly from outlet 80 to pump inlet 84 so the adhesive can flow
to pump inlet 84 under the force of gravity.
In the illustrative embodiment of FIGS. 1-4, the pump 86 is a
metered gear pump that is drivingly coupled with a motor 88, via a
drivetrain indicated generally at 90. The motor 88 can be a servo
motor and the drivetrain 90 can include a gear box 92 receiving a
rotatable output shaft (not shown) of the motor 88 and a coupling
94 disposed between the gear box 92 and the pump 86. The motor 88
and associated drivetrain control the speed of pump 86. Pump 86 may
be mounted on manifold 40. In the illustrative embodiment, pump 86
is attached to manifold 40 by conventional fasteners such as bolts
87 which pass through a housing of pump 86 and into manifold 40.
Alternatively, other pumps could be utilized, including piston
pumps.
A cover 97 is optionally provided that covers motor 86 and a
portion of drivetrain 90. A bracket 96 can be disposed in
surrounding relationship with a portion of the drivetrain 90 and
can be used to mount apparatus 10 to a portion of an overall system
for dispensing hot melt adhesive that can be a stationary structure
or a dedicated automation device.
The molten hot melt adhesive discharges from pump 86 through outlet
98 into a pump discharge passage 100 that is in fluid communication
at an opposite end with an inlet 102 of a dispenser 104. Dispenser
104 may be mounted directly on manifold 40. A pressure transducer
106 can be disposed in manifold 40 in fluid communication with the
pump discharge passage 100 so that it is effective for measuring
the pressure of the molten hot melt adhesive discharging from pump
86. Pressure transducer 106 can be electrically coupled to a
control panel (not shown) and can provide an annunciation or alarm
signal to an operator controlling apparatus 10 which advises the
operator that the pump discharge pressure of the molten adhesive is
outside of the desired operating range. Apparatus 10 can include a
filter 108 disposed in the pump discharge passage 100 to filter
fine particles of solid material that may exist within the molten
adhesive.
A suitable dispenser 104 is the model AG-900 gun module made by the
Nordson Corporation, which is a pneumatically operated module.
However, a wide variety of other pneumatically or electrically
operated guns can also be used that are made by Nordson Corporation
for extruding or potentially fiberizing hot melt adhesive. In the
illustrative embodiments, a source of pressurized air (not shown)
is supplied to a solenoid valve 110 (FIG. 1), which can comprise a
conventional 4-way solenoid valve. The dispenser 104 can include a
pneumatically actuated, reciprocating piston element 112 that
includes a disk 114 and a stem 116 integral with disk 114. The
piston element 112 can be biased in a closed position via spring
118 such that the stem 116 is disposed against valve seat 120,
thereby closing an outlet 122 of the gun 104.
A conduit 124, such as tubing, interconnects a port 126 on solenoid
valve 110 with a port 128 on the dispenser 104. Another conduit 130
interconnects a port 132 on solenoid valve 110 with a port 134 on
dispenser 104. Port 134 is in fluid communication with an internal
cavity 136 disposed proximate one side of the disk 114 and port 128
is in fluid communication with an internal cavity 138 disposed
proximate an opposite side of the disk 114. Accordingly, when an
operator wishes to open the dispenser 104, such that molten hot
melt adhesive can discharge through outlet 122, the solenoid valve
110 is operated to provide pressurized air to the internal cavity
138 and simultaneously vent cavity 136, such that a force is
exerted on disk 114 that overcomes the biasing force of spring 118
and lifts the reciprocating piston element 112 off of valve seat
120, thereby opening the dispenser 104. When an operator wishes to
close the dispenser 104, pressurized air is supplied to cavity 136,
while cavity 138 is simultaneously vented, via solenoid valve
110.
FIG. 5 illustrates an apparatus 150 for melting and dispensing hot
melt adhesive according to an alternative embodiment of the present
invention. Apparatus 150 is the same as apparatus 10 with the
following exceptions. Apparatus 10 includes a rotatable auger 152
disposed within a hopper 151. Both hopper 151 and auger 152 can be
made of an insulating material. For example, a polymeric material
having a relatively low thermal conductivity such as
polytetrafluoroethylene, commonly referred to as Teflon.RTM., can
be used. The auger 152 includes a shaft 154 and a helical blade 156
integral with the shaft 154. The blade 156 has a major diameter 158
that is substantially constant throughout the longitudinal length
of the auger 152. Accordingly, auger 152 is considered to be a
straight auger. Auger 152 is drivingly coupled with a motor 160
and, more particularly, a rotating output shaft 162 of motor 160 is
drivingly coupled with the shaft 154 of auger 152. A gear box (not
shown) and coupling (not shown) may be interposed between motor
160, which can be an electric motor, and auger 152 as required.
Alternatively, auger 152 can be driven by a pneumatic device. The
auger 152 is effective for moving the solid particles of the hot
melt adhesive around and along a longitudinal axis 159 of hopper
151 and through outlet 163 of hopper 151 into cavities 64.
The auger 152 is sized and configured with an appropriate pitch
such that the feed rate of the solid particles 56 into cavities 64
is greater than the melt rate of particles 56 within cavities 64.
This produces a desired back pressure on the hot melt adhesive
within cavities 64 to increase the melt rate and fluid momentum as
it is dispensed. Hopper 151 includes a side mounted inlet port 164
formed therein and including an inlet 166 effective for receiving
the solid particles 56 of hot melt adhesive therethrough. The hose
20 of the adhesive supply system 18 can be coupled to the inlet
port 164 and communicates with inlet 166. A plurality of apertures
168 are formed in the inlet port 164 and are effective for
exhausting pressurized air entering the inlet port 164 from hose
20, in the same manner as discussed previously with respect to
apertures 34 of apparatus 10. Hopper 151 has a lower portion 170
with a peripheral flange 172 that are the same as the lower portion
28 and peripheral flange 42 of apparatus 10. Hopper 151 further
includes an upper portion 174 that includes the inlet port 164. A
level sensor such as the previously discussed sensor 54 (not shown
in FIG. 5) can be disposed in the upper portion 174 such that a
distal end of the level sensor is disposed within an interior
chamber 176 of hopper 151. The remaining features and functions of
apparatus 150 are the same as apparatus 10 discussed
previously.
In another alternative embodiment, the pump 86, motor 88 and
drivetrain 90 can be omitted from apparatus 150. In this case, the
outlet (not shown in FIG. 5) of the collector passage 78 is in
fluid communication with the inlet 102 of the dispenser 104.
Pressure transducer 106 and filter 108 can also be included in this
embodiment.
FIG. 6 illustrates another apparatus 200 for melting and dispensing
hot melt adhesive according to the present invention. In this
embodiment, auger 152 is replaced with an auger 202 having a shaft
204 and a helical blade 206 integral with the shaft 204. As with
auger 152, auger 202 can be made of an insulating material. For
example, a polymeric material having a relatively low thermal
conductivity such as polytetrafluoroethylene, commonly referred to
as Teflon.RTM., can be used. The blade 206 includes a major
diameter 208 that is tapered outwardly from top to bottom and
accordingly, auger 202 is considered to be a tapered auger. The
structural features and functions of apparatus 200 are otherwise
the same as apparatus 150. Since the major diameter 208 of blade
206 is smaller proximate the inlet port 164, additional space is
provided to receive the solid particles 56 of hot melt
adhesive.
During operation of apparatus 10, feed system 18 automatically
maintains a pre-determined level of the solid particles 56 of the
hot melt adhesive within hopper 12 based on feedback provided by
level sensor 54. The feed system 18 may operate independently of
the operation of motor 88, pump 86 and dispenser 104. A controller
(not shown), which can be a programmable logic controller for
instance, associated with a parent machine, such as the
subsequently discussed dedicated automation device 300 illustrated
schematically in FIG. 11, sends an "ON" signal to the controller
(not shown), such as a programmable logic controller, associated
with motor 88 and dispenser 104 when it is desired to dispense the
molten or fluid hot melt adhesive out of dispenser 104. This
controller then sends synchronized signals to motor 88, to start,
and to the solenoid valve 110 causing dispenser 104 to open. These
signals can be synchronized so that dispenser 104 is opened before
motor 88 and pump 86 are turned on to avoid damage to dispenser 104
that could occur if motor 88 and pump 86 would be turned on before
dispenser 104 is opened. One or more time delay relays can be used
to synchronize opening dispenser 104 and then turning on motor 88
and pump 86. The molten hot melt adhesive is then discharged from
dispenser 104 onto a workpiece, for example the window sash 256
illustrated in FIGS. 7 and 8 or the filter 290 illustrated in FIGS.
9 and 10.
The operation of apparatus 150 and apparatus 200 are the same as
apparatus 10, when pump 86, motor 88 and drivetrain 90 are
included, except that the included augers 152 and 202,
respectively, force the particles 56 out of hopper 151, instead of
the particles discharging from hopper 151 solely by gravity as is
the case with hopper 12 of apparatus 10.
The apparatuses 10, 150 and 200 of the present invention can be
used in a wide variety of applications, with the use of these
apparatuses being particularly advantageous in those applications
having relatively low dispense or discharge rates, for example
dispense rates of about 1 lb/hr of hot melt adhesive. Apparatus 10
minimizes the "residence time" of the hot melt adhesive within
apparatus 10 prior to dispensing the hot melt adhesive from
dispenser 104. More particularly, the "residence time" of the hot
melt adhesive within apparatus 10 is less than the pot life of the
hot melt adhesive, thereby at least minimizing charring problems
associated with the hot melt adhesive. As used herein, "residence
time" is the time the hot melt adhesive is in a molten state.
The following features of apparatus 10 contribute to the
minimization of residence time of the hot melt adhesive within
apparatus 10. Hopper 12 is un-heated and may be made of a material
having a relatively low thermal conductivity, i.e., a material
having a relatively low coefficient of conductive heat transfer.
Further, the hopper 12 is disposed external of heated manifold 40.
Although hopper 12 may be mounted on heated manifold 40, the clamp
44, which is made of an insulating material, may be used to receive
the peripheral flange 42 of hopper 12 to mount hopper 12 on heated
manifold 40 and to discourage heat transfer from the heated
manifold 40 to hopper 12. As a result of the foregoing, the hot
melt adhesive within hopper 12 is generally not melted and remains
in a solid state (although some softening may occur). The solid hot
melt adhesive, such as particles 56, is discharged into manifold 40
on an "on-demand" basis in response to dispensing the molten hot
melt adhesive from dispenser 104.
The total combined volume of all of the cavities 64 and the heating
capacity of heating elements 62 are selected so that the melt rate
of heated manifold 40 is greater than, but relatively close to, the
dispense rate of the hot melt adhesive. For example, in one
embodiment apparatus 10 may have a dispense rate of about 1 lb/hr
and the melt rate of manifold 40 may be about 2 lbs/hr to about 4
lbs/hr. When a metered gear pump is used, such as pump 86, a
precise metered amount of molten thermoplastic material discharges
from pump 86 and flows through pump discharge passage 100 to the
inlet 102 of dispenser 104. In view of the foregoing dispense and
melt rates, hopper 12 may be relatively small. For example, in one
embodiment hopper 12 may have an overall length of about eight
inches and may have an inside diameter of about one to two inches
within the intermediate portion 30 of hopper 12. Inner surface 58
may be tapered as discussed previously. Therefore, the inside
diameter may vary somewhat within the intermediate portion 30 of
hopper 12 and the lower portion 28 of hopper 12. The maximum
outside dimension of the intermediate portion 30 varies with the
corresponding inside diameter and therefore may be about two to
three inches, for example. Accordingly, apparatus 10 more closely
approximates an ideal goal of "melting upon demand", as compared to
various conventional hot melt dispensing systems having melt rates
which can significantly exceed, for example, by an order of
magnitude or more, the associated dispense rate.
Dispenser 104 is closely coupled to the heated manifold 40 and may
be mounted on manifold 40. This results in essentially achieving
melting at the point of application, i.e., where the molten hot
melt adhesive is dispensed onto a workpiece. Accordingly, the
necessity of having a heated hose extending between a heated
manifold or other heated reservoir and an associated, remotely
mounted dispenser, is eliminated by the use of apparatus 10.
FIGS. 7, 8 and 11 illustrate one low dispense rate application
where the apparatus of the present invention, such as apparatus 10,
150 or 200, can be used to strengthen the corner joint bonding of
pultruded windows. FIG. 7 illustrates a window 250 having a frame
252 that can be mounted to a wall of a structure (not shown) and a
pane of glass 254 secured by a window sash 256, which in turn is
secured to the window frame 252.
Windows can be made of various materials with the window corner
members secured to one another using different methods. For
example, corner members of vinyl windows may be welded, corner
members of aluminum windows may be mechanically fastened and corner
members of wood windows may be joined using adhesive or mechanical
fasteners. Pultruded window corners, i.e., corners of windows
constructed of a fiber-reinforced composite, such as corner 258 of
window sash 256 illustrated in FIG. 8, are bonded with an adhesive,
such as a hot melt adhesive.
Pultruded window corners, such as corner 258, include an inner core
constructed of composite wood or fiberglass. Wood veneer or vinyl
profiles are laminated to the inner core. The structural integrity
of the corner, such as corner 258, is critical and this structural
integrity can be achieved by injecting the corner 258 with hot melt
adhesive as follows.
The corner 258 joins a vertical member 260 of sash 256 with a
horizontal member 262 which are placed in abutting relationship
with one another and then bonded together. As shown in FIG. 8,
vertical member 260 includes an aperture 264 that extends from the
outer surface of member 260 into the interior of member 260.
Aperture 264 is in fluid communication with a channel 266, located
in the interior of member 260, and a channel 268 formed in the
interior of member 260 and extending into the interior of member
262. While channels 266 and 268 are shown as forming a 90.degree.
angle therebetween, they can be formed at different angles relative
to one another and different numbers of channels can emanate from
aperture 264. Other configurations and combinations of various
numbers of apertures and channels may also be used. Sash 256
includes two of the vertical members 260, two of the horizontal
members 262 and four corners 258, each formed by joining one of the
vertical members 260 to one of the horizontal members 262. Each of
the corners 258 may include the aperture 264 and channels 266 and
268, oriented appropriately for the particular corner 258.
The heated manifold 40, hopper 12, pump 86 and dispenser 104 of
apparatus 10, 150 or 200 may be mounted on the dedicated automation
device 300, illustrated schematically in FIG. 11. Mounting hopper
12, pump 86 and dispenser 104 on heated manifold 40 provides a
compact unit that minimizes the space required to mount these
components on a dedicated automation device such as device 300. The
space required is further minimized due to the relatively small
size of hopper 10 and heated manifold 40 as compared to some
conventional systems having relatively large tanks or other
reservoirs of molten thermoplastic material. This is illustrated
schematically in FIG. 11 for apparatus 10, with the un-heated hose
20 coupled to hopper 12 as discussed previously. After aligning
dispenser 104 with aperture 264 formed in the vertical member 260
of window sash 256, the molten hot melt adhesive may be dispensed
from dispenser 104 and injected into and through aperture 264 and
into channels 266 and 268, thereby bonding members 260 and 262 of
window sash 256 to one another when the molten hot melt adhesive
cools and solidifies.
The members of additional corners 258 of window sash 256 can be
bonded in a similar manner with the alignment of dispenser 104 and
the corresponding aperture 264 in one of the members of sash 256
being achieved by changing the relative positions of dispenser 104
and window sash 256. This may be achieved by moving dispenser 104,
as well as the other components of apparatus 10 mounted on device
300, so as to change the position of dispenser 104, or by
repositioning window sash 256, using various conventional devices
known in the art. As a further alternative, multiple apparatuses
10, 150, or 200 may be mounted on device 300, with each being used
to bond the two members of one of the corners 258 of sash 256 to
one another. In this event, the multiple apparatuses 10, 150 or 200
may be manifolded together with respect to the supply of the solid
particles of hot melt adhesive, with the dispenser 104 of each
apparatus being aligned with the corresponding aperture 264 of
window sash 256.
The apparatus of the present invention, such as apparatus 10, 150
or 200, can be used in conjunction with the foregoing methodology
to bond members of window corners that are not pultruded window
corners, i.e., window corners made from a construction different
than a fiber reinforced composite. Additionally, adhesive may also
be applied to the abutting surfaces of members 260 and 262.
FIGS. 9 and 10 illustrate another application where the apparatus
of the present invention, such as apparatus 10, 150 or 200, can be
used to create a side seam 280 of a filter 290 shown in FIG. 9,
where filter 290 may be an oil filter for a motor vehicle for
example. Filter 290 is constructed of a filter material 282 that is
formed into a plurality of pleats 284 disposed about the periphery
of filter 290, from a flat sheet or block of the filter fabric. The
pleated block is then formed into the cylindrical shape shown in
FIG. 9, with the ends of the pleated block disposed in abutting
relationship. The heated manifold 40, hopper 12, pump 86 and
dispenser 104 may be mounted to the dedicated automation device 300
as illustrated schematically in FIG. 11. Dispenser 104 may then be
aligned with the two ends of filter 290 and seam 280 can be formed,
bonding the two ends of the pleated block together, by dispensing
the molten hot melt adhesive from dispenser 104 onto one or both of
the two ends of the pleated block. The molten hot melt adhesive may
flow along the abutting surfaces of the two ends. When the molten
hot melt adhesive cools and solidifies, a structurally sound seam,
or joint, is created. A center tube assembly (not shown) may then
be inserted in the interior 286 of filter 280. In use, the fluid to
be filtered flows through the center tube assembly and radially
outwardly through a plurality of holes (not shown) formed about the
periphery of the center tube assembly and then through filter
280.
While the foregoing description has set forth preferred embodiments
of the present invention in particular detail, it must be
understood that numerous modifications, substitutions and changes
can be undertaken without departing from the true spirit and scope
of the present invention as defined by the ensuing claims. The
invention is therefore not limited to specific embodiments as
described, but is only limited as defined by the following
claims.
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